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5 Sheets-Sheet 1 Filed May 15, 1958 ...ummm

WALLACE E. DIETRICH BY mmwJDnTx sept. 1o, 1963 W E DETRCH JR 3,103,578

DIGITIZED ANALOG COMPUTER Filed May l5, 1958 5 Sheets-Sheet 2 v INVENTOR.

l. WALLACE E. DIETRICH, JR. FIG. 2. BY

ATTORNEYS.

Sept. 10, 1963 w. E. DIETRICH, .JR

DIGITIZED ANALOG COMPUTER 5 Sheets-Sheet 3 Filed May 15, 1958 R-lO R- AMPLIFlfsR POT. ,2o

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y-VOLTAGE x-VOLTAGE Sept. 10, 1963 w. E. DIETRICH, .JR

DIGITIZED ANALOG COMPUTER 5 Sheets-Sheet 4 Filed May l5, 1958 INVENTOR.

WALLACE E. DlETR|cH,JR. BY

,a .4. zwfw/ ATTORNEYS.

Sept 10 1963 w. E. DIETRICH, JR

DIGITIZED ANALOG COMPUTER 5 Sheets-Sheet 5 Filed May l5, 1958 FIG. 6.

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INVENTOR. WALLACE E. DIETR\CH,JR. BY

ATTORNEYS.

United States Patent Ohce 3,103,578 Patented Sept. 10, 1963 3,103,578 DIGITIZED ANALOG COMPUTER Wallace E. Dietrich, Jr., Baltimore, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed May 15, 1958, Ser. No. 735,653

9 Claims. (Cl. 23S-151) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a digitized analog :computer for measuring and calculating the `characteristics of variious curves and shapes, such as ship hulls, for volume and stability values.

The invention comprises a curve tracer for physically tracing an arbitrary curve on a sheet of paper, a means connected to the curve tracer for generating a plurality of outputs proportional to the value of the curve along a pair of right-angled axes, and a means for calculating the desired characteristics of the curve such as the area or the moment of area with respect to any axis. ln addition, the slope of the curve may be obtained by differentiation.

The invention also embodies a novel method for calculating the product of several quantities, which quantities need not be related. Complex computation may be performed with the addition of suitable memory devices.

In the past, analog and digital computers have been used to calculate these areas and products, but have had numerous disadvantages.

Both types of computers have used input equipment such as photo-followers or manually scaling x and y coordinate values which are inaccurate and require many time-consuming adjustments.

Analog computers add by using resistor summing networks and multiply with D.C. amplifiers. The inherent inaccuracy and drift of these devices led many people to try digital computers for improved accuracy.

Digital computers vgenerally comprise large and expensive machines which are dicult to program. Mathematical formulas which describe complex curves soon lead to programming and machine time which are prohibit-ively long and expensive. Furthermore, many very useful curves such as for ship hulls do not lend themselves to any known mathematical analysis. Special purpose digital computers, Which are smaller and less expensive, in most instances lack the ilexibility to perform a variety of mathematical operations and generally must be designed for the particular operation to be performed.

A primary object of this invention is to disclose a digitized analog Vcomputer which will quickly and accurately integrate or multiply one or more variables.

Another object of this invention is to disclose a computer which will measure and calculate the area and rnoment of area of any arbitrary curve,

Another object of this invention is to disclose a curve tracer which will generate an output which is an accurate function of an arbitrary curve.

Another object of this invention is to disclose an analog to digital `conversion unit which is accurate, simple, and inexpensive to manufacture.

Other objects and advantages of the invention Will hereinafter become more fully apparent from the following description of the annexed drawings, which illustrate a preferred embodiment, and wherein:

FIG. 1 is a block diagram of the digitized analog computer.

FIG. 2 illustrates typical waveforms of the type used in the digitized analog computer.

FIG. 3 is a schematic diagram, partly in block forrn, of the computer.

FIG. 4 is a plan view of the curve tracer used with the computer.

FIG. 5 is a `detailed `view of the curve tracer taken on lines V-V of FIG. 4 looking in the direction of the arrows and showing the X-impulse generator.

FIG. `6 is a view, partly in sect-ion, taken on the line VI-VI of FIG. 4 looking in the direction of the arrows and showing the X-coordinate `carriage slide and supports.

FIG. 7 is a view, partly in section, taken along the lines VII-VH of FIG. 4 looking in the direction of the arrows and showing the Y-coordinate carriage.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. l (which illustrates a preferred embodiment) a curve tracer 10 having a curve 12` of any arbitrary shape drawn thereon. A set of coordinate axes marked X and Y are shown displaced by a '90 angle.

rPwo arrow-s 14 and 16 for the X and Y coordinates, respectively, indicate the position of a tracer point (not shown). In operation, the tracer point is moved by hand along the length of the curve and a pair of potentiometers 18 (for X) and 20 (for Y), which are connected as indicated by the `dotted lines `from the tracer point, apply a varying D.C. voltage to linear frequency oscillators 22 and 24, respectively.

As the stylus is moved along the curve, a series of X- pulses, spaced 40 to the inch, are generated by a switch 26 which is operated by a ratchet bar (#82, see FIG. 5) parallel to the X-axis. These X-pulses, which may be iiltered, amplified, etc. by suitable circuitry (not shown) are fed to a set of X-counters 28 where a number proportional to the 1distance that the stylus is moved along the X-axis is totaled.

The curve tracer 10 is disclosed on FIGS. 4 7 and described further on in the specification.

The varying D.C. voltage from the Y potentiometer 2i) is fed to the linear frequency oscillator 24 which generates a plurality of limpulses having -a frequency proportional to the Y amplitude of the curve i2 and having a constant amplitude.

The X-pulses are also fed to a Ifixed pulse time generator 3l) which generates a series of rectangular pulses having a fixed duration, which `duration is set by potentiometer 32, and where each pulse has a constant amplitude.

The outputs `of :oscillator 24 and generator 30 are fed to `area gate 34 where the number of the plurality of impulses from linear oscillator 24 which are generated during the duration of such pulse from the xed pulse time generator 30 are passed to the area counters 36. Since the number of the plurality of impulses is proportional to Y and the number of pulses from generator 30 is proportional to X, the area counters 36 register a number proportional to the area under the curve 12.

Simplified, illustrative waveforms are shown in FIG. 2 where an arbitrary 'curve 38 is plotted with respect to axes Y `and X. As the tracer point is moved along the curve 38, the output voltage rom the potentiometer 2.0 varies the `output of the linear frequency oscillator 24 in a fashion indicated by the number 24 on FIG. 2. At the same time a series of pulses having a fixed duration from the xed pulse time :generator 30, as indicated by 30 on FIG. 2, Iare generated. Area gate 34 passes the positive peaks of the impulses from oscillator 24, which are generated during the duration of each pulse from generator 30 asl indicated by number 34 on FIG. 2 and which are registered on area counters 36 as shown by number 36 on FIG. 2, where the sum is 9 units.

This sum `of 9` units is not exactly the area under the curve, but .a mathematic approximation to the correct value could, be imade by using Simpsons rule or other mathematical' approximations.' Lf 'a suciently large number of X pulses are 'generated' or the rate of change of the value of Y from one X pulse to the next is small, the total on the area counter 36 will, yafter proper calibration, register the correct value of the area. In this case, as described above, avalue of 40 pulses per inch of X distance was used.

In actual practice somewhat more convenient values are used. Suppose a square area of l inches by 10 inches is desired to tbe measured. Oscillator 24 will vary from 100 c.p.s. at Y=0 to 100 kc. at Y=l0. There will be 40 pulses per inch times 10 inches equals 400 pulses generated by the X pulse generator 30. If onesecond X pulses are generated, varea counter 36will total 400 times 100 kc. equals 40 l06, after the tracerV pointr is moved across the x 10 tarea. In addition, a. time of 400 seconds wouldbe required for this operation.

In order to achieve theV proper total, area counter 36 could be divided by 1 6.-- l0O/40X 10 4X 1075.

In this case each X pulse will have a du-ration of 2.5 milliseconds. and the area counters 36 wil-l read 100,000 whichis divided by -a factor of 1000 to give the true value of 100. In addition the tracer point may beV moved very rapidly so that a total real time of 400 times 2.5,

milliseconds equals. one second is all that is needed for the measurement and' calculation of the 10 x 10 area. Other measurements suchas the moment of the area with respect to the X 'axis may be made by feeding the Y potentiometer 20 output to a variable pulse time generator 40, which generates .a pulse initiated by switchr26, which pulse has a duration proportional-to Y'anda constant amplitude. The output of generator 40 and the output of oscillator 24 (by means of switch 42) are fed tomoment gate 44 and the number of impulses from oscillator 24 generated during the duration of each of the series of 'pulses `from' generator 40 is totaled on moment counters 46.

v As indicated on FIG. 2, the variable durationl pulse is shown at 40 andra total proportional to the moment of area of 29l is shown at 46. Oscillator 24 has an output frequency proportional to Y and generator 40 has a frequency output proportional to X and a time duration proportional to Y so that the moment counters 46 read avalue proportional to YYX or Y2AX which is proportional to the moment of areawithrespect Ito the X axis.

The correct equation is ,4 so that the value 29 should be divided by 2 or be 14.5, which value is more nearly .the correct moment of area of the example shown in FIG. 2.

The moment of Iarea with respect to the Y axis, which is proportional to XY AX, may be obtained by placing switch 42 in the other position to connect moment gate 44 to linear frequency oscillator 22. Calibration of the V moment counters 46 may be performed by adjusting the duration of the pulse from the variable pulse time generator 40 or by varying the frequency of the oscillators 22 and 24 `as described in connection with the area counter 36.

Since the output of larea gate 34 is Ia quantitative measresults inthe slope of the curve between these two points. Suitable memory circuits and subtracting counters m'aybe necessary as is well known to those skilled in the art.

A particular circuit for performing lthe functions of the elements in PIG. 1 is shown in FIG. 3, partly in block form. The Y potentiometer 20 passes its output to cathode follower V2. From one half of the tube V2 the signal passes to linear frequency oscillator 24. Oscillator 24 is a free-running multivibrator type having feedback from the grid Aof V4 through cathode follower VS and condenser C3 to resistor R6. The charging of condenser C3 by means of diode V6 varies the cutoff time of V4 -and thereby linearizes the output frequency of oscillator 24 withrespect to the input voltage from V1 in addition to the simple variation of the cut-olf time by the voltage fed from V1 through V6. v

The output of oscillator 24, which is an alternating frequency having sharp peaks, isY fed to ampliiier 48 Comprising cathode follower V7 and pentode amplifier V8. The positive peaks of the output of oscillator 24 are clipped by the grid circuit of V8 and the negative peaks are amplified, inverted, `and sentl to area gate 34 and to switch 42.

'I'he output of V1 is sent to variable pulse time generator 40 randtoY calibrating meter 50, which will enable generator 40 to be set by R17 to various values depending on the area under the curve 38 and the necessary scale factors which are used in ship design. Generator 40 isV a phantastron circuit for generating a variable pulse width similar tothat described in The Phantastron, by Wm. L. Roberts, Radio Engineering, November 1954, pp. 12J-14. Cathode follower tu'beiV12 and associated circuit provides a low impedance, reference voltage source for the control and suppressor grids of V10.

The XV pulses from switch 26 comein through con-- denser C8 land act to trigger generator 40 for a length oftime proportional to the voltage from potentiometer 20 Via V1 and R14. The output pulse of generator 40 is sent to amplifier 52 having cathode follower-amplifierl tive pulse fromgenerator 401allows the right hand section to operate asl an amplifier to the X or Y pulses.

'Ihe xed pulse time generator 30 is similar to variable pulse generator 40 except that the equivalent R14 resistor goes toiaviariable potentiometer R26, which is set to la particular value lduring a computation instead of being continuously variable.

Linear frequency oscillator 22 is similar to linear frequency oscillator 2'4 and area gate 34' is similar to moment gate 44 and therefore these units are shown in block form. The .area and moment counters 36 and 46 are Berkeley Counters 705A by Beckman Instruments, Inc., of Richmond, California.

In this particular embodiment the voltage values are as shown in the drawings and the circuit values are as follows:

V12 12AU7 V1, 2, 3, 4, 5, 7 1/2-l2AU7 V6, 9, 11 1/2-6AL5 V8 6BA6 V10 6AS6 V13, 14 5963 R1, 2 ohms 150K R3, 5 do 36K R4 do 330K R18 do 27K R19 do 4.7K R23, do 20K R24 do 39K R28 do 390K R32, 6, 17, 29 megohms l R30, 26, 7, 13, 27 ohms 100K R8, 20, 21 do 270K R9 do 62K R10 do 15K R34, 31, 11, 14 do 47K R12 do 68 R15, 33 clo 470K R16, 22 do v10K C1, 13 microfiarads .001 C2 micro-micro-faradsn l() C3 microfarads .l C4 micro-microfarads 47 C5 microiarads 25 C6 do 4 C7 do .l5 C8 micro-microfarads 270 C9 microfarads-- .066 C10-l2 micro-micro-frarads" 20 N51, 2, 3 NESl Meter Sil-Triplett model 227-2", 0 50 microamps. with series resistors calibrated for O*l-5--l0-100 volts.

Referring to FIG. 4, a plan view of `the curve tracer 10 is shown having an aluminum base plate 56 which is approximately square of `about inches on a side and being 3A inch thick. A pair of aluminum supports 58 are mounted at two adjacent corners of the base plate 56. Each support has a hole 60 for mounting a 1/2 inch diameter stainless steel smooth shaft 62 and a hole 64 for mounting a 1/z inch diameter stainless steel ratchet bar 66, which bar has a grooved surface of 40' threads per inch cut thereon.

An X coordinate carriage 68 made of aluminum is shown comprising a hexagonal sleeve 70, a tracer wheel 72 driving `a potentiometer 18, and an X carriage rail unit 76 between the sleeve 7 (l and the wheel 72.

Referring also to FIG. 6, the sleeve 70 has a central hole 78 having a pair of ball :bearings 80 mounted therein which run smoothly on shaft 62.

referring also to FIG. 5, a stainless steel pawl 82 having a sharpened end 84, which is intermittently operated by ratchet bar 66, is pivotally mounted on the sleeve 70 by pin 85. An operating lend 86 of pawl 82 operates 'a microswitch 26 which is attached to sleeve 70` to produce a series of X pulses as the X carriage is moved along shaft 62.

Referring to FIG. 4, the X potentiometer 18 is attached to a bracket 88 mounted on X carriage rail unit 76, which also allows the potentiometer shaft to be connected to the tracer wheel 72. Wheel 72, which has a sharp, beveled ledge to cut through dust and dirt and not ride up and down, .rolls on a rail 90 mounted on the lower edge of the -base plate 56. The potentiometer 18 is a 3 turn Helipot, Series C of 50,000 ohms made by the Beckman Instruments, Inc., of Richmond, California.

The X carriage rail unit 76 comprises ,a central section 91 having `a number of lightening holes 92, which section 91 is integral with la pair of Y carriage rails 94 which extend across the base plate 56.

A Y carriage 96 moves along the Y carriage rails 94 on a pair of rollers 98 and on a tracer wheel 100, which wheel also drives a Y potentiometer 20 supported by a bracket 104 on carriage 96. Y potentiometer 20 is a 50,000 ohm potentiometer, #8519601] by G. M. Giannini and Co., East Orange, NJ. A plurality of rollers 106 are mounted on the Y carriage 96 with their axes at right angles to one of the carriage rails 94 and on each side thereof. These rollers 106 press against the rail 94 from each side and prevent any transverse movement of the Y carriage unit 96 with respect to the X carriage 68 as is more clearly illustrated in F IG. 7.

Again referring to FIG. 7, a tracer point holder 108 made of ya clear plastic, such `as methyl methacrylate sold under the trademark Lucite, is attached to the Y carriage 96 by means of screws 110. A stainless steel tracer point L12 having a handle 1.14 is placed in a hole drilled in the holder 108.

In operation the X carriage 68 is moved to the left of the curve 12 land the Y carriage 96, which is mounted on the X carriage 68, yis moved below the curve 12. The tracer point 112 is placed Vat the lower left hand corner of the curve and moved by hand along the curve 12. The tracer point moves the Y carriage along the Y oarriage rails 94 and moves the X vcarriage 68 to the right by means of rollers 106. An X pulse output is obtained from the microswi'tch 26 and the X and Y potentiometers generate appropriate outputs for the digitized analog computer.

The curve 12 may 4be made to a yconvenient scale such as 1A equals 1 foot for ship hull design.

It should 4rbe understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention fand that tit is intended to icover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

l. A `digital multiplication unit for multiplying two variables together comprising an oscillator for generating a number of impulses having an output frequency proportional to a variable input to said oscillator, a pulse generator for generating a set of pulses having la duration proportional to a variable and means for multiplying said variables together by counting ythe number of irnpulses generated during the duration of each pulse of said set of pulses whereby a product may be obtained.

2. A digital multiplication unit according to claim l but further characterized by said last named means comprising `a gate connected to said oscillator and pulse generator and a counter `connected to said gate whereby the product may be displayed.

3. A digital multiplication unit according to claim 2 but further characterized by said oscillator comprising a multivibrator and said pulse generator comprising a phantastron.

4. A digital multiplication unit laccording to claim 1 but further characterized by means for generating a linear input to said oscillator from a mechanical movement.

5. A digitized analogue `computer for iinding the moment of an area under :a curve comprising an oscillator for generating a plurality of (impulses having a frequency proportional to the value of said curve along a irst reference axis, a pulse generator for generating la series of pulses proportionally spaced along a second reference axis of said curve Iand having a duration propoi-tional to the value of said curve along said rst axis, and means for calculating the moment of area of said curve with respect to said second axis by `coun-ting the number of impulses generated tduriug the duration of each of said series of pulses.

6. A digitized analogue computer according to `claim 5 but further characterized by said last named means cornprising a gate connected to said oscillator and pulse generator and a counter connected to said gate whereby the moment may be displayed.

7. A digitized analogue computer for finding the moment of an area under a curve comprising an oscillator for genenating a plurality of impulses having a frequency proportional to the value of said curve along a rst reference axis, fa pulse generator for generating a series of pulses proportionally spaced along a second reference axis of said curve and having a duration proportional to the value 'of said curve lalong said axis, and means for calculating fthe moment of area of said curve with respect to said first axis by counting the numlber of impulses fo saidplurality yof impulses generated during the duration of each of said series of impulses.

8. A digitized analogue computer according to claim 7 but funther characterized by said last named means comprising :a gate connected to said oscillator and pulse generator land a counter connected to said gate whereby the moment of area may be displayed. f

' 9. A digitized analogue :computer for finding the area under a curve comprising a base plate for mounting a curve wlrose characteristics are to be measured, an X- coordinate carriage movably supported on saidv base along a rst Aaxis of said curve, means for generating a series of pulses hav-ing a constant duration and spaced along said iirst axis'connected to said X-coordinate carriage, fa Y-eoordinate carriage supported by said X-coordinate carriage and movable yalong a second axis of said curve, means for generating a plurality of impulses having an output frequency proportional to the vaine of said curve along said second axis connected to said Y- coordinate carriage, 'and means connected to both of said generating means for calculating the area yunder lsaid curve by counting the number tof said plurality of impulses generated during rthe `duration of each of said series of pulses.

References Cited'in the le of this patent UNITED STATES PATENTS 

9. A DIGITIZED ANALOGUE COMPUTER FOR FINDING THE AREA UNDER A CURVE COMPRISING A BASE PLATE FOR MOUNTING A CURVE WHOSE CHARACTERISTICS ARE TO BE MEASURED, AN XCOORDINATE CARRIAGE MOVABLY SUPPORTED ON SAID BASE ALONG A FIRST AXIS OF SAID CURVE, MEANS FOR GENERATING A SERIES OF PULSES HAVING A CONSTANT DURATION AND SPACED ALONG SAID FIRST AXIS CONNECTED TO SAID X-COORDINATE CARRIAGE, A Y-COORDINATE CARRIAGE SUPPORTED BY SAID X-COORDINATE CARRIAGE AND MOVABLE ALONG A SECOND AXIS OF SAID CURVE, MEANS FOR GENERATING A PLURALITY OF IMPULSES HAVING AN OUTPUT FREQUENCY PROPORTIONAL TO THE VALUE OF 